JPH082106A - Marking composition and laser marking method - Google Patents

Abstract

PURPOSE:To obtain a sharp black color by the irradiation with laser beam by constituting a marking compsn. of an energy beam curable resin, a leuco dye low in toluene solubility and a coupler. CONSTITUTION:A marking compsn. contains an energy beam curable resin, a leuco dye low in toluene solubility and a coupler. The energy beam curable resin is an ultraviolet curable resin and the solubility of the leuco dye with respect to toluene at 25 deg.C is 5w/v% or less. This leuco dye is a fluorane compd. represented by formula (wherein R1 and R2 are a methyl group or an ethyl group, X is fluorine or chlorine and n is an integer of 0-2).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a marking composition and a laser marking method for imparting a clear mark to a surface of a molded material by irradiating it with a laser beam.

[0002]

2. Description of the Related Art In recent years, electronic parts such as ICs, resistors, capacitors and inductors, electric parts such as relays, switches, connectors and printed circuit boards, housings for electric products, automobile parts, machine parts, cables, sheets and packaging. Sheets, cards, labels, various containers for food or pharmaceuticals,
A printing method using a marking ink has been widely used for marking characters or symbols such as a manufacturer name, an article name, a manufacturing date, a lot number, etc. on a surface of a container such as a cap. This method requires a long time from the process of printing to the drying of the ink, the difficulty of marking fine parts,
Since there are problems such as maintenance of print quality, complexity of management, and high cost, rationalization thereof is desired.

Recently, in order to rationalize marking, a laser marking method has been used in which the surface of a component or the like is directly irradiated with laser light and a part of the surface is etched by thermal decomposition or evaporation for marking. However, in this marking method, since there are various materials for the parts to be marked, there is a problem in that clear marking cannot be performed depending on the material, or in the case of a colored material, it is difficult to obtain a clear mark. have.

As a method for solving the above-mentioned problems, a method of applying a laser-markable UV-curable resin to the surface of a marking object such as an electronic component, an electric component, a housing, a package, etc., and curing it, and then marking with a laser beam It has been known. This method has an advantage that it requires only a short process and enables fine marking, and good marking can be obtained.
However, when a commercially available ultraviolet curable resin is used, there is a drawback that the obtained mark disappears due to oil adhesion depending on what is to be marked. Furthermore, in the case of ink that is colored by laser, especially black,
Conventionally, heavy metal-containing compounds such as lead have been used as color formers, but there are problems such as environmental pollution due to heavy metals and unclear marks. A system using a leuco dye and a developer known as a thermal recording material is considered as a material that develops black color without using a heavy metal that causes environmental pollution. When a system using an agent is applied, it has a drawback that it gradually develops color even when it is not irradiated with laser light (referred to as background fog).

[0005]

DISCLOSURE OF THE INVENTION In a composition for laser marking using an ultraviolet curable resin, even a system using a leuco dye and a color developer does not cause background fog and develops a clear black color, and is more robust. There is a need for a marking composition that is highly accurate.

[0006]

The inventors of the present invention have reached the present invention as a result of intensive studies to solve the above-mentioned problems. That is, the present invention provides (1) a marking composition containing an energy ray-curable resin, a leuco dye having low solubility in toluene and a developer, and (2) the energy ray-curable resin is an ultraviolet ray curable resin. The marking composition according to (1) above, and (3) the leuco dye having a low solubility in toluene are leuco dyes having a solubility in toluene at 25 ° C. of 5 w / v% or less.
The marking composition of (4), the leuco dye is represented by the formula (1)

[0007]

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(In the formula (1), R ₁ and R ₂ represent a methyl group or an ethyl group, X represents a fluorine or chlorine, and n is 0.
Represents an integer of 2; ) A marking composition of (1) or (3), which is a fluoran compound represented by
The leuco dye is 2,2-bis (4- (6 '-(N-cyclohexyl-N-methylamino) -3'-methylspiro (phthalide-3,9'-xanthene) -2'-ylamino) phenyl) propane. The marking composition according to (1) or (3) above, (6) the marking composition according to (1) above, wherein the developer has a low solubility in toluene, and (7) solubility in toluene. Low-developing agent
The marking composition according to the above (6), which is a developer having a solubility in toluene at 65 ° C. of 10,000 ppm or less,
(8) Solubility in toluene at 65 ° C is 10,000 p
The marking composition according to the above (7), wherein the developer having a pm or less is a sulfonylphenol type developer, a methylenebisphenol type developer, or a phenol polymer.
The marking composition according to (7) above, wherein the developer having a solubility in toluene at 65 ° C. of 10,000 ppm or less is a 4,4′-sulfonyldiphenol-based developer having a substituent or a phenol polymer. 10) The marking composition according to the above (9), wherein the substituent of the 4,4′-sulfonyldiphenol-based developer having a substituent is an alkyl group, a halogen atom or an allyl group.

(11) The marking composition according to (1) above, wherein the developer has a low solubility in toluene and a solubility in water at 25 ° C. of 3 ppm or less.
(12) 2,2 ′, which has a low solubility in toluene and a solubility in water at 25 ° C. of 3 ppm or less,
6,6'-tetramethyl-4,4'-sulfonyldiphenol, 2,2 ', 6,6'-tetrabromo-4,
The marking composition according to (11) above, which is a 4'-sulfonyldiphenol or a phenol polymer, (13) the marking composition according to (12) above, wherein the phenol polymer is a poly-p-vinylphenol, (14). UV curable resin, leuco dye described in (4) above and (12) above
Marking composition containing one or more of the color developers described in (15), UV curable resin, leuco dye described in (5) above, and marking containing one or more color developers described in (12) above. (16) A laser marking method, which comprises irradiating a laser beam on a cured coating layer of the marking composition of (1), (14) or (15), which is formed on the surface of an article. 17) The article is a bottle, a cap, a card, a label or a can as described above (1)
6) the laser marking method, (18) a color-forming composition containing a leuco dye and a developer, wherein the developer is 2,2 ', 6,6'-tetramethyl-4,4'-sulfonyldiphenol , 2,2 ', 6,6'-Tetrabromo-4,4'-sulfonyldiphenol or poly-p-
A coloring composition which is a vinylphenol.

The energy curable resin used in the present invention may be any resin curable by energy rays such as infrared rays, visible light rays, ultraviolet rays and electron beams, and preferably any resin curable by ultraviolet rays, Examples thereof include radical polymerization type or cationic polymerization type resins, but radical polymerization type resins are preferable.

The radical-polymerization type resin includes various acrylate monomers, oligomers, polyether type, unsaturated polyester type, epoxy type, urethane type,
Polybutadiene-based, polyacetal-based, polyester /
Examples include various urethane-based acrylate monomers and oligomers. Examples of the acrylate monomers include trimethylolpropane triacrylate, dipentaerythritol pentaacrylate, trimethylolpropane ethoxytriacrylate, trimethylolpropane propoxytriacrylate, tripropylene glycol ethoxydiacrylate, neopentyl glycol alkoxydiacrylate, neopentyl glycol. Propoxy diacrylate, tripropylene glycol diacrylate, polyethylene glycol diacrylate, bisphenol A ethoxy diacrylate, bisphenol A propoxy diacrylate, 1,6-hexanediol diacrylate, 1,4-butanediol diacrylate, stearyl acrylate, phenol ethoxy Monoacrylate, nonyl E Nord ethoxy monoacrylate, 2-phenoxyethyl acrylate,
Examples thereof include monomethoxytripropylene glycol monoacrylate, monomethoxyneopentyl glycol propoxymonoacrylate, monomethoxytrimethylolpropane ethoxydiacrylate, dicyclopentenyloxyethyl acrylate and dicyclopentenyl acrylate. Examples of the acrylate oligomers include epoxy acrylate oligomers such as epoxidized soybean oil acrylate, acrylates based on various bisphenol A type epoxy resins, epoxidized linseed oil acrylate, and modified bisphenol A diacrylate.
Formula (3)

[0012]

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Polyester acrylate oligomers such as reaction products of polyesters and acrylic acid based on dibasic acids and aliphatic diols as shown in formula (4)

[0014]

[Chemical 4]

Examples thereof include aliphatic or aromatic urethane acrylates obtained by reaction with aliphatic or aromatic isocyanates based on the polyols or polyesters shown in (1).

As the cation-polymerizable resin, various aliphatic, alicyclic and aromatic epoxy resins are used. Particularly preferred are acrylates of monohydric and polyhydric alcohols and epoxy resin acrylates. Urethane acrylate monomers and their oligomers.

In the marking composition of the present invention, it is preferable to use a photoinitiator for curing. Examples of such an initiator include thioxanthone type, anthraquinone type, acetophenone type and benzoin for radical polymerization type resins. Known photoinitiators such as ether-based and benzophenone-based,
In addition, known photoinitiators such as aromatic diazonium salts, aromatic halonium salts, aromatic sulfonium salts, and metallocene compounds are used for the cationic polymerization type resin. These photoinitiators may be used alone or in combination of two or more. Further, when a cationic polymerization type resin is used for curing, 80 to 1
It is desirable to heat in the range of 70 ° C, particularly preferably in the range of 100 to 150 ° C. The heating time varies depending on the temperature, but is usually between 5 and 30 minutes.

The leuco dye used in the present invention is preferably a leuco dye having a low solubility in toluene, for example, the leuco dye represented by the formula (1) or 2,2-bis (4-).
(6 '-(N-cyclohexyl-N-methylamino)-
3'-Methylspiro (phthalide-3,9'-xanthene) -2'-ylamino) phenyl) propane (solubility in toluene at 25 ° C is 0.055 w / v%; trade name Papyrole SD-120 Showa Denko KK ) Etc. Examples of the leuco dye represented by the formula (1) include 3-diethylamino-7-o-fluoroanilinofluorane, 3-dimethylamino-7-o-fluoroanilinofluorane, and 3-diethylamino-7-p. -Fluoroanilinofluorane, 3-dimethylamino-7-p-fluoroanilinofluorane, 3-diethylamino-7-
o-chloroanilinofluorane, 3-diethylamino-
7-p-chloroanilinofluorane, 3-diethylamino-7-p-chloro-o-fluoroanilinofluorane, 3-dimethylamino-7-p-fluoro-o-chloroanilinofluorane, 3-diethylamino -7-
2 ′, 4′-dichloroanilinofluorane and the like can be mentioned, but particularly preferred is 3-diethylamino-7-o.
-Fluoroanilinofluorane (solubility in toluene at 1.45 w / v% at 25 ° C), 3-dimethylamino-7-o-fluoroanilinofluorane, 3-diethylamino-7-o-chloroanilinofluorane , 3-diethylamino-7-p-chloroanilinofluorane. Specifically, the solubility in toluene has a solubility in toluene at 25 ° C., preferably 5 w / v.
% (Weight / volume%, the same applies hereinafter) or less, more preferably 3
A leuco dye of w / v% or less, and more preferably 2 w / v% or less is preferable. It is considered that these fluoran compounds are less likely to cause background fog because they have a low solubility in the energy ray curable resin. If the amount used is too small, a clear mark cannot be obtained, and if it is too large, there is no difference in the sharpness of the mark and it is wasteful in terms of cost. The amount is preferably about 5 to 50% by weight, more preferably about 7 to 45% by weight.

Examples of the color developer usable in the present invention include 4,4'-sulfonyldiphenol (insoluble in toluene, solubility in water: 1000 ppm at 25 ° C.), bis- (3-allyl-4-hydroxyphenyl). Sulfone (insoluble in toluene, solubility in water 5p at 25 ℃
pm), 2,2 ', 6,6'-tetramethyl-4,4'
-Sulfonyldiphenol (insoluble in toluene and water),
2,2 ', 6,6'-Tetrabromo-4,4'-sulfonyldiphenol (insoluble in toluene and water), 4-
(4'-isopropoxyphenyl) sulfonylphenol (Solubility in toluene at 65 ° C is 2000 pp
m, a solubility in water at 25 ° C. of 1980 ppm) and other sulfonylphenol type developers, 4,4′-isopropylidenediphenol (solubility in toluene is 65
7,000ppm at ℃, solubility in water at 25 ℃ 38
00ppm), bis- (p-hydroxyphenyl) methane, 1,1-bis- (p-hydroxyphenyl) -cyclohexane, and other methylenebisphenol type developers, p-
Hydrocarbon-based monophenol developers such as octylphenol and p-phenylphenol, benzyl p-hydroxybenzoate, dimethyl 4-hydroxyphthalate, diethyl 5-hydroxyisophthalate, 3,5-di-tert.
-Butylsalicylic acid, salicylic acid, a phenolic aromatic carboxylic acid derivative such as benzyl β-hydroxynaphthalenecarboxylate and a polyvalent metal salt of a phenolic aromatic carboxylic acid, preferably a sulfonylphenol type developer, more preferably Is preferably a 4,4'-sulfonyldiphenol-based developer having a substituent on the phenol nucleus. Examples of the substituent include C _{1 to} C such as methyl group.
₅ alkyl group, halogen atom such as bromine atom, allyl group, etc., and the number of substitution is 1 to 4, preferably 1 to 2 per phenol nucleus, and the substitution position is The ortho position of the hydroxyl group is preferred.

A phenol polymer can also be used as a developer. This phenol polymer is insoluble in toluene or water, and is, for example, a homopolymer of p-vinylphenol (Marka Linker M: Maruzen Petrochemical Co., Ltd.), a copolymer of p-vinylphenol and 2-hydroxyethyl methacrylate. Combined (Maruka Linker CHM: Maruzen Petrochemical Co., Ltd.)
Co., Ltd., a copolymer of p-vinylphenol and methyl methacrylate (Marka Linker CMM: Maruzen Petrochemical Co., Ltd.)
Manufactured by Maruzen Petrochemical Co., Ltd., a copolymer of p-vinylphenol and styrene (marker linker CST:
Maruzen Petrochemical Co., Ltd., copolymers of p-vinylphenol and phenylmaleimide, copolymers of p-vinylphenol and maleic acid, and copolymers of p-vinylphenol and fumaric acid. Phenols (all of these polymers are manufactured by Maruzen Petrochemical Co., Ltd.), copolymers of dicyclopentadiene and phenol, copolymers of dicyclopentadiene and cresols, and dicyclopentadiene and diphenol. Examples thereof include copolymers.

Of these developers, those having a low solubility in toluene are preferred. Specifically, the solubility in toluene has a solubility in toluene of 65
C., preferably 10,000 ppm or less, more preferably 5000 ppm or less, still more preferably 3000 ppm
The following developers are good. In addition, when scratch resistance is required, such as when the product is easily bent such as a packaging sheet or when the marks are easily contacted with each other, 4,4′-sulfonyldiphenol-based compounds having a substituent group are used. The color developer and the phenol polymer type color developer are preferable. Furthermore,
When hot water resistance is required, such as when it is applied to hot water sterilization treatment such as milk or canned beverages, it hardly dissolves in water (for example, the solubility in water is about 3 p at 25 ° C).
A color developer is preferable. These color developers are used alone or in combination of two or more kinds. The amount of the developer used for the leuco dye is 30 to 3 for the leuco dye.
Although it is 00% by weight, 50 to 200% by weight is preferable.
The most preferable color developer is one that is hardly dissolved in toluene or water, for example, 2,2 ', 6,6'-tetramethyl-4,4'-sulfonyldiphenol, 2,2',
Examples thereof include phenol polymers such as 6,6′-tetrabromo-4,4′-sulfonyldiphenol and poly-p-vinylphenols.

Other additives may be added to the laser marking composition of the present invention, if desired. Examples of other additives that can be used include, in addition to sensitizers for increasing color development sensitivity, fillers, colorants, dispersants, flow regulators, release agents, flame retardants, lubricants, light stabilizers, Examples include materials used for coating an ultraviolet curable resin such as an antioxidant.

Examples of the sensitizer include higher fatty acid amides such as stearic acid amide, animal waxes such as beeswax and shellac wax, vegetable waxes such as carnauba wax, and mineral waxes such as montan wax.
Paraffin wax, petroleum wax, higher fatty acid esters, chlorinated paraffin, synthetic paraffin, acetoacetic acid anilides, diphenylamines, carbazoles, fatty acid anilides, carboxylic acid esters such as dimethyl terephthalate and diphenylphthalate, benzene sulfonic acid anilide, etc. Sulfonic acid amides, p-toluenesulfonic acid phenoxyethyl ester, benzenesulfonic acid phenyl ester and other sulfonic acid esters, bis- (4-allyloxyphenyl) sulfone, bis- (4-pentylphenyl) sulfone and other diphenyls Naphthol derivatives such as sulfones, 1-benzyloxynaphthalene, 2-benzoyloxynaphthalene, urea derivatives such as N-stearyl urea, 4-acetylacetophenone, Kutadekan -2,17- diketone compounds such as dione is used. The amount used is usually 0.5 part to 2 parts with respect to 1 part of the color developer.

Examples of the filler that can be used in the present invention include inorganic fillers such as calcium carbonate, silica, alumina, mica, calcium silicate, clay, talc, glass fiber and carbon fiber, and polyethylene, polyamide and epoxy resin. , Organic fillers such as guanamine resin. Examples of usable coloring agents are carbon black, phthalocyanine, monoazo, disazo, quinacridone, anthraquinone, flavanthrone, perinone, perylene, dioxazine, condensed azo, azomethine or methine organic dyes, titanium oxide, lead sulfate. , Zinc oxide,
Inorganic pigments such as iron black, chrome yellow, zinc yellow, chrome vermilion, red iron oxide, cobalt purple, ultramarine blue, dark blue, chrome green, and cobalt green can be mentioned. The amount of the filler used is usually 80 w / w% or less based on the total solid content, and in the case of a colorant, 3% w / w% or less based on the total solid content.

The marking composition of the present invention comprises an ultraviolet curable resin, a leuco dye and optionally a sensitizer, a filler,
Colorants, dispersants, flow regulators, release agents, flame retardants, lubricants,
A "leuco dye ink" prepared by mixing a light stabilizer, an antioxidant and the like with a stirring device such as a three roll, preferably at a temperature of 15 to 30 ° C, an ultraviolet curable resin and a color developer. Agent and optional sensitizers, fillers, colorants, dispersants, flow regulators, release agents, flame retardants, lubricants, light stabilizers, antioxidants, etc. using a 3-roll agitator Then, it preferably comprises a "developing ink" prepared by mixing at a temperature of 5 to 30 ° C, and both are uniformly mixed before use.

To carry out the laser marking method of the present invention, for example, the following may be carried out. That is, the marking composition of the present invention is applied to a substrate to be marked (usually applied so as to have a film thickness after curing of 10 to 100 μm) and irradiated with energy rays to be cured. After molding according to the following, carbon dioxide laser light on the surface of the coated article,
By irradiating with YAG laser light, excimer laser light, etc., black marking with clear contrast can be obtained. As the irradiation amount of laser light, for example, in the case of a pulsed carbon dioxide gas laser, an irradiation amount of 0.5 to ⁶ J / cm ² is adopted. Examples of the base material include polyesters such as polyethylene terephthalate and polybutylene terephthalate,
Plastic films made of vinyl chloride, polyethylene, polypropylene, etc., commonly used plastic plates of these materials, acrylic resin, ABS resin, etc., metal plates of aluminum, iron, etc., evaporated paper, coated paper, synthetic paper, etc. Papers are included. The marking composition of the present invention is a sheet, a packaging sheet, a card, a label, a bottle, various containers such as food and medical products such as caps and metallic cans, and a manufacturer name, content indication on the surface of caps of containers, etc. Made date,
Used to display lot number etc.

[0027]

EXAMPLES Next, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples. The raw materials used in the examples are as follows.

A: Epoxy acrylate (KAYARA
DR-011 manufactured by Nippon Kayaku Co., Ltd. B: Triacrylate (KAYARAD TMPTA)
Nippon Kayaku) C: Monoacrylate (KAYARAD 2-HEMA)
Nippon Kayaku) D: 1-hydroxycyclohexyl phenyl ketone E: 2,4-diethylthioxanthone F: 2-ethylanthraquinone G: 1,4-dimethoxybenzene H: flow regulator (trade name: Modaflow Monsanto Chemical) I : Diallyl phthalate resin J: 3,3-diethylamino-7-o-fluoroanilinofluorane (solubility in toluene at 25 ° C. is 1.14 w / v%) K: 3,3-diethylamino-7-o-chloroani Rinofluorane (Solubility in toluene at 25 ° C
8 w / v%) L: 3,3-dibutylamino-6-methyl-7-anilinofluorane (solubility in toluene is 1 at 25 ° C.
7.5 w / v%) M: 3,3-dibutylamino-7-o-fluoroanilinofluorane (Solubility in toluene is 1 at 25 ° C.
0.5w / v%)

N: bis- (3-allyl-4-hydroxyphenyl) sulfone (insoluble in toluene, solubility in water: 5 ppm at 25 ° C.) O: 4,4'-sulfonyldiphenol (insoluble in toluene, solubility in water) Is 1000 ppm at 25 ° C.) P: 4,4′-isopropylidenediphenol (solubility in toluene is 7000 ppm at 65 ° C., solubility in water is 3800 ppm at 25 ° C.) Q: 2,2 ′, 6,6′-tetramethyl -4,4'-Sulfonyldiphenol (insoluble in toluene and water) R: 2,2 ', 6,6'-Tetrabromo-4,4'-sulfonyldiphenol (insoluble in toluene and water) S: Poly p- Bromide of vinylphenol (Markalinker MB, insoluble in toluene and water, softening point 210 ° C, manufactured by Maruzen Petrochemical Co., Ltd.) T: 4- ( '- isopropoxyphenyl) sulfonyl phenol (degree be dissolved in the toluene 2 at 65 ° C.
000ppm, solubility in water at 25 ℃ 1980p
pm) U: 2,2-bis (4- (6 '-(N-cyclohexyl-N-methylamino) -3'-methylspiro (phthalide-3,9'-xanthene) -2'-ylamino) phenyl) propane (Solubility in toluene is 0.055w / v% at 25 ° C)

Examples 1 to 11 and Comparative Examples 1 and 2 An acrylate composition having the formulation shown in Table 1 below was uniformly mixed by a three-roll mill, and each of (a) "leuco dye ink" and (b) "visible". Colored ink "was obtained. Then, both of them were uniformly mixed in a ratio of 1: 1 ((a) :( b) = 1: 2 in Example 3) to obtain a marking composition of the present invention. This was coated on an iron plate with a bar coater so that the film thickness after curing was 20 μm, and then the composition was cured by irradiating it with ultraviolet rays from a high pressure mercury lamp to obtain a test piece. A pulse-type carbon dioxide laser irradiator (manufactured by Laser Technics, BLAZAR6000, energy density 3 J /
cm ² ), when a laser beam was irradiated, clear black marks were obtained in Examples 1 to 11, but not in Comparative Examples 1 and 2. The numbers in Table 1 mean parts by weight.

[0031]

[Table 1] Table 1 Examples Inks Resins Colorants Color developers Others No. ABCD EFGH I 1 (a) 60 40 J: 30 3 0.3 0.3 1 (b) 60 40 N: 30 3 0.3 0.3 1 2 (a) 60 40 J: 30 3 0.3 0.3 1 (b) 60 40 O: 30 3 0.3 0.3 1 3 (a) 70 30 J: 20 3 2 0.3 1 5 (b) 70 30 P: 20 3 2 0.3 1 5 4 (a) 60 40 K: 30 3 0.3 0.3 1 (b) 60 40 N: 30 3 0.3 0.3 1 5 (a) 60 40 J: 30 3 0.3 0.3 1 (b) 60 40 Q: 30 3 0.3 0.3 1 6 (a) 60 40 J: 30 3 0.3 0.3 1 (b) 60 40 R: 30 3 0.3 0.3 1 7 (a) 60 40 K: 30 3 0.3 0.3 1 (b) 60 40 Q: 20, R: 10 3 0.3 0.3 18 (a) 60 40 J: 30 3 0.3 0.3 1 (b) 60 40 S: 30 3 0.3 0.3 19 (a) 60 40 J: 15, K: 15 3 0.3 0.3 1 (b) 60 40 T: 30 3 0.3 0.3 1 10 (a) 60 40 U: 30 3 0.3 0.3 1 (b) 60 40 N: 30 3 0.3 0.3 1 11 (a) 70 30 J: 20 3 2 0.3 1 5 (b) 70 30 R: 20 3 2 0.3 1 5 Comparative example 1 (a) 60 40 L: 30 3 0.3 0.3 1 (b) 60 40 N: 30 3 0.3 0.3 1 2 (a) 6 0 40 M: 30 3 0.3 0.3 1 (b) 60 40 N: 30 3 0.3 0.3 1

Performance Test Results Using the test pieces obtained in Examples 1 to 11 and Comparative Examples 1 to 2, pulse type carbon dioxide laser irradiator (manufactured by Laser Technics, BLAZAR6000 energy density 3 J / cm was used. ² ) is used to irradiate a laser beam to make a black mark, 1) the background fog, 2) the color density,
3) sharpness, 4) scratch resistance, 5) water resistance, 6) hot water resistance, and 7) plasticizer resistance were evaluated. A coloring agent having a low solubility in toluene was used, and a coloring agent prepared according to the formulation described in Comparative Example in Table 1 was used as a control. The results are shown in Table 2 below.

[0033]

[Table 2]

1) Ground fog: Color density value measured by a Macbeth reflection densitometer RD-914 type after curing and before laser light irradiation 2) Color density: Macbeth reflection densitometer RD- at the marking portion of the test piece Color density value measured with 914 type 3) Sharpness: Visual judgment of readability of mark ◯: Good sharpness x: Poor sharpness (generally, the smaller the background fog, the higher the coloring density is, the more excellent the sharpness is. ) 4) Scratch resistance: After curing, it is visually judged whether or not there is a trace of color development on the background after scratching the test piece before laser light irradiation with a nail. ◯: No color development ×: Color development 5) Water resistance: Marked After the test piece was immersed in tap water at room temperature for 72 hours, the color density value of the mark part measured with the above Macbeth reflection densitometer 6) Hot water resistance: The marked test piece was immersed in water at 80 ° C for 30 minutes. Erase Visual judgment of color condition
◯: No bleaching x: Completely bleaching 7) Plasticizer resistance: The marked test piece was sandwiched from both sides with a PVC wrap film, and 300 gr / cm
Color density value measured by the above Macbeth reflection densitometer after leaving for 15 hours at 40 ° C under the load of ^2.

As is clear from the 3) sharpness data in Table 2, the sharpness is good in the examples, and it can be seen that the composition of the present invention is suitable for laser marking.
That is, although the example is significantly superior to the comparative example,
This was carried out while the ratio of the color density of the portion not irradiated with the laser beam of 1) in Table 2 to the color density of the portion irradiated with the laser beam of 2) in Table 2 was around 2: 1 in the comparative example. That in the example is supported by the fact that the ratio is large, around 10: 1. From the comparison between Comparative Examples 1 and 2 and Examples 1, 4 and 10 using the same color developer, the solubility of the leuco dye used as the color developing agent in the Examples in toluene was 25 ° C. and both were 2% or less. On the other hand, the solubility of the leuco dye used as the color former in toluene in Comparative Example is 10% at 25 ° C.
From the above, it is considered that the effect of the present invention is an effect due to the use of a leuco dye having low solubility in toluene.

Next, looking at the data of 4) scratch resistance in Table 2, the data of Examples 1, 4 to 8, 10 and 11 are superior to the data of Examples 2, 3 and 9. . From the comparison between Examples 1 and 2 and Examples 3 and 11, it is considered that the influence of the color developer is large.

Further, looking at the data of 6) hot water resistance in Table 2, the data of Examples 5-8, 10, 11 are superior to the data of Examples 1-4, 9. This is because although the difference in water resistance at room temperature in 5) in Table 2 is not recognized, the phenomenon that the color disappears in the latter with hot water, so that the solubility of the developer used in the latter in water varies with temperature. It is considered that it increased significantly with the rise and melted into hot water, whereas the former did not have such a phenomenon.

[0038]

EFFECTS OF THE INVENTION A marking composition which has a small background fog and develops a vivid black color when irradiated with a laser beam, and a marking composition which develops a vivid black color and has excellent fastness are obtained.

Claims (18)

[Claims] 1. A marking composition comprising an energy ray curable resin, a leuco dye having a low solubility in toluene and a developer. 2. The marking composition according to claim 1, wherein the energy ray curable resin is an ultraviolet curable resin. 3. The marking composition according to claim 1, wherein the leuco dye having a low solubility in toluene is a leuco dye having a solubility in toluene at 25 ° C. of 5 w / v% or less. 4. A leuco dye is represented by the formula (1): (In the formula (1), R ₁ and R ₂ represent a methyl group or an ethyl group, X represents fluorine or chlorine, and n represents an integer of 0 to 2). Item 1 or the marking composition of item 3. 5. The leuco dye is 2,2-bis (4- (6'-
(N-Cyclohexyl-N-methylamino) -3'-methylspiro (phthalide-3,9'-xanthene) -2 '
The marking composition according to claim 1 or 3, which is -ylamino) phenyl) propane. 6. The composition for laser marking according to claim 1, wherein the developer has a low solubility in toluene. 7. A developer having a low solubility in toluene,
The marking composition according to claim 6, which is a developer having a solubility in toluene at 65 ° C of 10,000 ppm or less. 8. The solubility in toluene at 65 ° C. is 100.
The marking composition according to claim 7, wherein the developer having a concentration of 00 ppm or less is a sulfonylphenol type developer, a methylenebisphenol type developer, or a phenol polymer. 9. Solubility in toluene at 65 ° C. is 100.
The color developing agent having a content of 00 ppm or less has a substituent 4,
The marking composition according to claim 7, which is a 4'-sulfonyldiphenol-based developer or a phenol polymer. 10. The marking composition according to claim 9, wherein the substituent of the 4,4′-sulfonyldiphenol-based developer having a substituent is an alkyl group, a halogen atom or an allyl group. 11. The marking composition according to claim 1, wherein the developer has a low solubility in toluene and a solubility in water at 25 ° C. of 3 ppm or less. 12. Low solubility in toluene, and 2
The color developer whose solubility in water at 5 ° C is 3 ppm or less is 2,
2 ', 6,6'-tetramethyl-4,4'-sulfonyldiphenol, 2,2', 6,6'-tetrabromo-
The marking composition according to claim 11, which is 4,4'-sulfonyldiphenol or a phenol polymer. 13. The marking composition according to claim 12, wherein the phenolic polymer is poly-p-vinylphenol. 14. A marking composition comprising an ultraviolet curable resin, one or more of the leuco dye according to claim 4 and the color developing agent according to claim 12. 15. A marking composition comprising an ultraviolet curable resin, one or more of the leuco dye according to claim 5 and the color developer according to claim 12. 16. The method according to claim 1, which is formed on the surface of an article.
A laser marking method comprising irradiating a cured film layer of the marking composition of 4 or 15 with a laser beam. 17. The laser marking method according to claim 16, wherein the article is a bottle, a cap, a card, a label or a can. 18. A color-forming composition containing a leuco dye and a developer, wherein the developer is 2,2 ′, 6,6′-tetramethyl-4,4′-sulfonyldiphenol, 2,
A color-forming composition which is 2 ', 6,6'-tetrabromo-4,4'-sulfonyldiphenol or poly-p-vinylphenols.